c# - 从具有多个条件的数据表中选择

Question

我正在尝试从数据表中选择一行，该行具有特定帐号且最近日期早于或等于设置的日期时间。我想要下面但只有最新的条目所以我似乎想在 currentDateTime 之后使用 FirstOrDefault() 或 SingleOrDefault() (即...... <= currentDateTime.FirstOrDefault())

DateTime currentDateTime = firstDate;
while (firstDate <= lastDate)
{
     foreach (AccountCategory a in db.AccountCategories)
     {
         var result = Settings.dtCurrent.AsEnumerable()
               .Where(b => b.Field<string>("Account") == a.Account 
                         && (b.Field<DateTime>("Date") <= currentDateTime);
     }
}

上面没有给我最新的条目。

Answer 1

这样试试

    DateTime currentDateTime = firstDate;
    while (firstDate <= lastDate)
    {
         foreach (AccountCategory a in db.AccountCategories)
         {
             var result = Settings.dtCurrent.AsEnumerable()
                   .Where(b => b.Field<string>("Account") == a.Account 
                             && (b.Field<DateTime>("Date") <= currentDateTime).OrderByDescending(b=> b.Field<DateTime>("Date")).FirstOrDefault();


   }
}